1. Technical Field
This disclosure is directed to integrated circuits, and more particularly, to the detection of power transients within integrated circuits.
2. Description of the Related Art
Integrated circuits (IC's) are typically tested at the end of the manufacturing process in order to verify their correct operation and to identify parts that are faulty. In addition, IC's may be tested during the design phase in order to find flaws in the design that are not apparent before it is committed to silicon.
Many different failure mechanisms may cause a particular instance of an IC to fail a test. In some cases, the failures may be hard failures. Examples of hard failures include faulty or inoperative transistors, unintentional short circuits, unintentional open circuits, and so forth. In other cases, failures may be soft failures. A soft failure may be defined as a failure that occurs in the operation of a circuit even though the components themselves are not faulty.
One source of soft failures is transients on supply voltage nodes. For example, the switching of a large number of circuits simultaneously can cause a momentary drop in the supply voltage (sometimes referred to as a droop, a glitch, or a di/dt event). As a result of the momentary drop in the supply voltage, some transistors may switch states when they are not intended to, while others may not switch states even though such switching is intended. Thus, even though the actual transistors of the IC meet specifications, a glitch in the supply voltage may nevertheless cause the IC to fail a test or otherwise enter an inoperative state from which the IC cannot recover.